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<title>Function make_expr</title>
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<a name="boost.proto.make_expr_idp89526624"></a><div class="titlepage"></div>
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<h2><span class="refentrytitle">Function make_expr</span></h2>
<p>boost::proto::make_expr &#8212; Construct an expression of the requested tag type with a domain and with the specified
          arguments as children.</p>
</div>
<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="../../proto/reference.html#header.boost.proto.make_expr_hpp" title="Header &lt;boost/proto/make_expr.hpp&gt;">boost/proto/make_expr.hpp</a>&gt;

</span>
<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Tag<span class="special">,</span> <span class="keyword">typename</span><span class="special">...</span> A<span class="special">&gt;</span> 
  <span class="keyword">typename</span> <a class="link" href="result_of/make_expr.html" title="Struct template make_expr">proto::result_of::make_expr</a><span class="special">&lt;</span><span class="identifier">Tag</span><span class="special">,</span> <span class="identifier">A</span> <span class="keyword">const</span><span class="special">...</span><span class="special">&gt;</span><span class="special">::</span><span class="identifier">type</span> <span class="keyword">const</span> 
  <span class="identifier">make_expr</span><span class="special">(</span><span class="identifier">A</span> <span class="keyword">const</span> <span class="special">&amp;</span><span class="special">...</span> a<span class="special">)</span><span class="special">;</span>
<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Tag<span class="special">,</span> <span class="keyword">typename</span> <a class="link" href="../../Domain.html" title="Concept Domain">Domain</a><span class="special">,</span> <span class="keyword">typename</span><span class="special">...</span> A<span class="special">&gt;</span> 
  <span class="keyword">typename</span> <a class="link" href="result_of/make_expr.html" title="Struct template make_expr">proto::result_of::make_expr</a><span class="special">&lt;</span><span class="identifier">Tag</span><span class="special">,</span> <span class="identifier">Domain</span><span class="special">,</span> <span class="identifier">A</span> <span class="keyword">const</span><span class="special">...</span><span class="special">&gt;</span><span class="special">::</span><span class="identifier">type</span> <span class="keyword">const</span> 
  <span class="identifier">make_expr</span><span class="special">(</span><span class="identifier">A</span> <span class="keyword">const</span> <span class="special">&amp;</span><span class="special">...</span> a<span class="special">)</span><span class="special">;</span></pre></div>
<div class="refsect1">
<a name="idp136258912"></a><h2>Description</h2>
<p>
            This function template may be invoked either with or without specifying a
            <code class="computeroutput">Domain</code> template parameter. If no domain is specified, the domain
            is deduced by examining domains of the given arguments. See
            <code class="computeroutput"><code class="computeroutput"><a class="link" href="deduce_domain.html" title="Struct deduce_domain">proto::deduce_domain</a></code></code> for a full
            description of the procedure used.
          </p>
<p>
            Let <code class="computeroutput"><em class="replaceable"><code>WRAP</code></em>(x)</code> be defined such that:
            </p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem"><p>
                  If <code class="computeroutput">x</code> is a <code class="computeroutput">boost::reference_wrapper&lt;&gt;</code>,
                  <code class="computeroutput"><em class="replaceable"><code>WRAP</code></em>(x)</code> is equivalent to
                  <code class="computeroutput"><code class="computeroutput"><a class="link" href="as_child_idp90952128.html" title="Function as_child">proto::as_child</a></code>&lt;Domain&gt;(x.get())</code>.
                </p></li>
<li class="listitem"><p>
                  Otherwise, <code class="computeroutput"><em class="replaceable"><code>WRAP</code></em>(x)</code> is equivalent to
                  <code class="computeroutput"><code class="computeroutput"><a class="link" href="as_expr_idp90940704.html" title="Function as_expr">proto::as_expr</a></code>&lt;Domain&gt;(x)</code>.
                </p></li>
</ul></div>
<p>
          </p>
<p>
            If <code class="computeroutput"><code class="computeroutput"><a class="link" href="wants_basic_expr.html" title="Struct template wants_basic_expr">proto::wants_basic_expr</a></code>&lt;typename Domain::proto_generator&gt;::value</code>
            is true, then let <code class="computeroutput"><em class="replaceable"><code>E</code></em></code> be
            <code class="computeroutput"><code class="computeroutput"><a class="link" href="basic_expr.html" title="Struct template basic_expr">proto::basic_expr</a></code></code>; otherwise,
            let <code class="computeroutput"><em class="replaceable"><code>E</code></em></code> be
            <code class="computeroutput"><code class="computeroutput"><a class="link" href="expr.html" title="Struct template expr">proto::expr</a></code></code>.
          </p>
<p>
            Let <code class="computeroutput"><em class="replaceable"><code>MAKE</code></em>(Tag, b...)</code> be defined as
            <code class="computeroutput"><em class="replaceable"><code>E</code></em>&lt;Tag,
            <code class="computeroutput"><a class="link" href="listN.html" title="Struct template listN">proto::listN</a></code>&lt;decltype(b)...&gt; &gt;::make(b...)</code>.
          </p>
<p>
            If <code class="computeroutput">Tag</code> is
            <code class="computeroutput"><code class="computeroutput"><a class="link" href="tag/terminal.html" title="Struct terminal">proto::tag::terminal</a></code></code>, then return
            <code class="computeroutput"><em class="replaceable"><code>WRAP</code></em>(a<sub>0</sub>)</code>.
          </p>
<p>
            Otherwise, return
            <code class="computeroutput">Domain()(<em class="replaceable"><code>MAKE</code></em>(Tag, <em class="replaceable"><code>WRAP</code></em>(a)...))</code>.
          </p>
</div>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2008 Eric Niebler<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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